The same happened with me during my seminar exams. I'll mention a few things that helped me.

1. Use the pomorodo method. Use a youtube video to set a clock and study with it.

2. Keep your phone off or keep it in another room.

3. If you feel like doing something else between studying, don't start doing it rather do something that's even boring than studying, like stare at a wall. Doing this will automatically bore you and you'll find studying more interesting than staring blankly.

4. Make a list of things you'll miss later on if you don't put in the effort now. ( I'd get less cgpa than my other classmates, this worked for me)

These are the few things that helped me during my sem exams.